weighted average cost of capital capital

wonderfuldream

WACC(weighted average cost of capital) is also referred to as MCC (marginal cost of capital).

This is where I am a bit confused.

When a question asks you to calculate WACC/MCC should you put any weight on a company's existing debt structure? Or do you only consider the weighting of the new debt the company is about to acquire?

Weighted average cost of capital sounds like you need to consider the cost of all debt, new and old.

Marginal cost of capital sounds like you only need to consider cost of new debt.

The answers to EOC questions are not consistent on this matter.